1. Field of the Invention
This invention relates to a semiconductor device, and more particularly to a semiconductor device having a pellet mounted on a radiating plate thereof and a method of manufacturing the semiconductor device.
2. Description of the Related Art
Conventionally, semiconductor devices such as an LSI (Large Scale Integrated Circuit) and a transistor chip are utilized in various electronic apparatus. In such apparatus as just mentioned, generally a pellet including a semiconductor circuit is encapsulated in a resin member, and a large number of lead terminals each formed from an elongated conductive plate are provided on the opposite sides of the resin member.
Since those lead terminals are connected to connection pads of the pellet in the inside of the resin member, if the semiconductor device is mounted on a circuit board and the lead terminals are connected to signal lines, then various signals can be inputted to and outputted from the pellet.
However, such a semiconductor device as described above inevitably generates heat when the pellet inputs/outputs a signal. For example, in a semiconductor device used for transmission of radiowaves of a portable telephone set, since it consumes a large amount of power, the pellet generates a large amount of heat. Therefore, it is required to radiate the heat efficiently.
In a semiconductor device disclosed, for example, in Japanese Patent Laid-open No. 209054/94, the radiating plate is exposed at a central portion thereof to the bottom of the resin member so that heat generated by the pellet may be radiated from the central portion of the radiating plate.
However, since the central portion of the radiating plate cannot be connected to a conductor pattern of the circuit board by solder, the effect of heat radiation at this position cannot be anticipated.
On the other hand, in another semiconductor device which is disclosed in Japanese Patent Laid-open No. 224326/94, the radiating plate is exposed at a central portion thereof to the bottom of the resin member and is exposed at four corner portions thereof to the top of the resin member so that heat generated by the pellet may be radiated from the central portion and the four corner portions of the radiating plate.
However, the four corner portions of the radiating plate exposed to the top of the resin member cannot be connected to conductor patterns of the circuit board by solder and cannot contribute very much to heat radiation.
Meanwhile, in a further semiconductor device which is disclosed in Japanese Patent Laid-open No. 63142/90, the radiating plate is exposed not only at a central portion thereof but also at an end portion thereof to the bottom of the resin member so that heat generated by the pellet may be radiated from the central portion and the end portion of the radiating plate.
However, while the end portion of the radiating plate exposed to the bottom of the resin member contributes to heat radiation since it can be connected to a conductor pattern of the circuit board by solder, this is not sufficient to achieve sufficient radiation of heat generated by the pellet.